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Biology 2e

Introduction

Biology 2eIntroduction
Photo shows a yellow seahorse with its tail curled around a fragment of coral.
Figure 43.1 Female seahorses produce eggs for reproduction that are then fertilized by the male. Unlike almost all other animals, the male seahorse then gestates the young until birth. (credit: modification of work by "cliff1066"/Flickr)

Chapter Outline

43.1 Reproduction Methods
43.2 Fertilization
43.3 Human Reproductive Anatomy and Gametogenesis
43.4 Hormonal Control of Human Reproduction
43.5 Human Pregnancy and Birth
43.6 Fertilization and Early Embryonic Development
43.7 Organogenesis and Vertebrate Formation

Animal reproduction is necessary for the survival of a species. In the animal kingdom, there are innumerable ways that species reproduce. Asexual reproduction produces genetically identical organisms (clones), whereas in sexual reproduction, the genetic material of two individuals combines to produce offspring that are genetically different from their parents.

Generally, the producers of sperm (the small gamete) are called males, producers of the eggs (the large gamete) are called females. Any other characteristics that may often be associated with sex, such as parental care or sexual behavior, are not universal throughout the animal kingdom. During sexual reproduction the male gamete (sperm) may be placed inside the female’s body for internal fertilization, or the sperm and eggs may be released into the environment for external fertilization. Seahorses, like the one shown in Figure 43.1, provide an example of the latter. Following a mating dance, the female lays eggs in the male seahorse’s abdominal brood pouch where they are fertilized. The eggs hatch and the offspring develop in the pouch for several weeks.

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